Laminate and packaging bag using the same

Abstract

To provide a laminate that has excellent material recyclability and suitability for bag-making.SOLUTION: A laminate comprising at least a substrate layer and a sealant layer is characterized in that the substrate layer is polyolefin having an MD heat shrinkage of less than 20.0% when heat-treated at 150°C, the sealant layer is made of polyolefin, a melting point of the sealant layer is lower than that of the substrate layer by 10°C or more, and a polyolefin content in the laminate is 90 mass% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a packaging laminate and a packaging bag using the same. [Background technology]

[0002] Packaging materials are made from a variety of materials, depending on the nature and quantity of the contents, post-processing to protect the contents from deterioration, the form in which the package is transported, the method of opening the package, and the method of disposal.

[0003] For example, stand-up pouches are becoming more widely used because they allow products to stand out on store shelves. To ensure that a stand-up pouch can be seen from all sides without bending, the laminate that makes up the pouch must be rigid. Furthermore, if the contents are liquid, the pouch must be strong enough not to break when dropped. To meet these requirements, laminates made up of a combination of polyester film, nylon film, polyolefin film, etc. have been used.

[0004] However, with the recent increase in awareness of environmental issues, various products are being required to have functions such as resource conservation and recycling, and similar functions are being required of laminates used in packaging.

[0005] One method for reusing laminates that combine various materials is to separate each material, but separating a laminate that has been given a certain strength as a package requires various thermal, chemical, and mechanical actions.Furthermore, to separate the separated materials, physical actions based on specific gravity and spectroscopic methods that differ for each material must be used, but the more precision one tries to achieve in this separation and sorting, the more energy one must consume, making it inefficient.

[0006] Another approach is to reconstruct the original laminate with materials of the same type and reuse the laminate as a single material. Thermoplastic resins, in particular, come in a variety of types, including polyolefins, polyesters, and polyamides. Each can be given various properties depending on the molecular weight, molecular weight distribution, heat treatment, orientation, stretching, and other conditions and processes. Polyolefins, in particular, have good processability due to their low melting point, and are easy to use because various materials are manufactured using copolymers, etc. For this reason, various methods have been proposed.

[0007] Patent Document 1 discloses a laminate for packaging materials comprising at least a substrate, an intermediate layer, and a heat-sealing layer, wherein the substrate, intermediate layer, and heat-sealing layer are made of the same material, the substrate and intermediate layer have been stretched, and the same material is polyolefin. In this invention, the polyolefin substrate is stretched to impart strength and heat resistance to the laminate, but if the entire laminate is made of polyolefin, the heat resistance is insufficient, and the laminate will distort during heat-sealing for bag production, resulting in defects. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2020-157715 Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide a laminate that is excellent in material recyclability and is suitable for bag manufacturing. [Means for solving the problem]

[0010] A first aspect for solving the above problem is a laminate including at least a base layer and a sealant layer, wherein the base layer is a polyolefin having an MD heat shrinkage of 10.0% or less when heat treated at 150°C, the sealant layer is a polyolefin, the melting point of the base layer is 10°C or more higher than that of the sealant layer, and the polyolefin content in the laminate is 90% by mass or more.

[0011] According to the first aspect, the laminate does not distort due to heat during bag production, and packaging bags can be obtained without dimensional deviation even when produced at high speed. Furthermore, since the polyolefin content in the laminate is 90% by mass or more, it can be recycled as a polyolefin resin, and has high material recycling suitability.

[0012] Furthermore, by providing a gas barrier layer between the base layer and the sealant layer, a laminate having gas barrier properties can be obtained.

[0013] In a second aspect of the present invention, there is provided a packaging bag formed by heat-sealing the sealant layer-forming surfaces of the laminate. According to this aspect, the laminate does not distort due to heat, and a packaging bag with no dimensional deviation can be obtained even when the bag is made at high speed.

[0014] A third aspect of the present invention is a packaging bag according to the second aspect, further comprising a polyolefin member sandwiched between the sealant layer-forming surfaces, wherein the polyolefin member and the sealant layer are made of the same resin.

[0015] According to the third aspect, a package can be obtained in which the laminate is not distorted by heat even in the vicinity of the heat-sealed portion of the polyolefin member, and the laminate is bonded with sufficient strength to maintain the contents and airtightness. [Effects of the Invention]

[0016] The laminate of the present invention has high suitability for material recycling and bag production. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing one embodiment of a laminate of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing another embodiment of the laminate of the present invention. [Figure 3] FIG. 2 is a cross-sectional view showing another embodiment of the laminate of the present invention. [Figure 4] FIG. 2 is a cross-sectional view showing another embodiment of the laminate of the present invention. [Figure 5] 1 is a schematic diagram of a spouted gusset pouch, which is one embodiment of the self-standing packaging bag of the present invention. [Figure 6] 1 is a schematic diagram of a standing pouch with a spout, which is one embodiment of the self-standing packaging bag of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Fig. 1 is a cross-sectional view of a three-layer laminate 10, one embodiment of the laminate of the present invention. The three-layer laminate 10 comprises a substrate 1, a gas barrier film layer 3, and a sealant layer 5. The substrate 1, gas barrier film layer 3, and sealant layer 5 are bonded together via adhesive layers 2 and 4, respectively. The gas barrier film layer 3 comprises a gas barrier film substrate 3-b and a gas barrier layer 3-a. The three-layer laminate 10 is configured such that the gas barrier layer 3-a is located on the substrate 1 side, and the gas barrier substrate 3-b is located on the sealant layer 5 side.

[0019] 2 is a cross-sectional view of a three-layer laminate 20, another embodiment of the laminate of the present invention. The three-layer laminate 20 comprises a substrate 1, a gas barrier film layer 3, and a sealant layer 5. The gas barrier film layer 3 comprises a gas barrier film substrate 3-b and a gas barrier layer 3-a. The difference from the three-layer laminate 10 is that the gas barrier substrate 3-b is located on the substrate 1 side, and the gas barrier layer 3-a is located on the sealant layer 5 side.

[0020] 3 is a cross-sectional view of a three-layer laminate 30, which is another embodiment of the laminate of the present invention. The three-layer laminate 30 comprises a substrate 1, a gas barrier film layer 3, and a sealant layer 5. The gas barrier film layer 3 comprises a gas barrier film substrate 3-b and a gas barrier layer 3-a. The difference from the three-layer laminate 20 is that the positions of the substrate 1 and the gas barrier film layer 3 are reversed.

[0021] When the laminate of the present invention is a three-layer laminate, either or both of the substrate 1 and the gas barrier substrate 3b are polypropylene. When either or both of the substrate 1 and the gas barrier substrate 3b are polypropylene, the polypropylene can be selected from the materials described below within the range of polypropylene. In the three-layer laminate, the adhesive layer 2 and the adhesive layer 4 are optional and can be omitted when the substrate 1 or the sealant layer 5 is formed on a layer directly adjacent to the substrate 1.

[0022] 4 is a cross-sectional view of a two-layer laminate 40, which is another embodiment of the laminate of the present invention. The two-layer laminate 40 includes a gas barrier film layer 3 and a sealant layer 5. The gas barrier film layer 3 includes a gas barrier film substrate 3-b and a gas barrier layer 3-a. The two-layer laminate 40 is configured such that the gas barrier layer 3-a is located on the sealant layer 5 side.

[0023] When the laminate of the present invention is a two-layer laminate, the gas barrier substrate 3b is polypropylene. When the gas barrier substrate 3b is polypropylene, it can be selected from the gas barrier substrate materials described below within the range of polypropylene. In addition, in the two-layer laminate, the adhesive layer 4 is an optional component, and can be omitted when the sealant layer 5 is formed directly on the gas barrier film layer.

[0024] [Base material layer] The base layer of the present invention is a polyolefin having an MD heat shrinkage of 10.0% or less when heat treated at 150° C. Examples of polyolefins include polyethylene and polypropylene.

[0025] Considering the suitability for vapor deposition processing, printing processing, bag making processing, filling suitability, etc., high-density polyethylene (HDPE) is an example of polyethylene constituting the substrate layer. In addition, to improve physical properties such as flexibility, a multilayer film formed by coextrusion, such as high-density polyethylene (HDPE) / medium-density polyethylene (MDPE) / low-density polyethylene (LDPE) / medium-density polyethylene (MDPE) / high-density polyethylene (HDPE), may be used as the substrate layer.

[0026] Examples of polypropylene include oriented polypropylene. Generally, polypropylene is broadly classified into homopolymers, random copolymers, block copolymers, and terpolymers, and the polymer type is selected depending on the application and required performance. However, when used as the base layer of a laminate, homopolymer polypropylene is preferred. A laminate having a homopolymer on the outermost surface or a polypropylene base material with a heat-resistant resin such as nylon laminated on the outermost surface and arranging the heat-resistant surface as the outermost layer has improved heat resistance, thereby reducing problems of false adhesion and insufficient seal strength due to insufficient temperature during bag production. Furthermore, for the purpose of imparting easy adhesion and sealability, a multilayer film having a homopolymer core layer and a copolymer or terpolymer formed as a skin layer by coextrusion may be used as the base layer.

[0027] The polyolefin film constituting the substrate layer may be a stretched film or a non-stretched film. However, from the viewpoints of impact resistance, heat resistance, water resistance, dimensional stability, etc., the polyolefin film may be a stretched film. This makes it possible to more suitably use the laminate in applications where hot filling or retort / boiling treatment is performed. The stretching method is not particularly limited, and any method may be used, such as inflation stretching, uniaxial stretching, or biaxial stretching, as long as it can provide a dimensionally stable film.

[0028] Among these, it is preferable to use biaxially oriented polypropylene, which has high rigidity and high heat resistance, and such polypropylene has an MD heat shrinkage rate of less than 20%, preferably 15% or less, and more preferably 10% or less when heat treated at 150°C.

[0029] The melting point of the polypropylene film is preferably higher than that of the sealant layer, by at least 10°C, and preferably by at least 20°C. The melting point of the base layer is preferably 150°C or higher, more preferably 160°C or higher. The melting point of the base layer can be measured using a differential scanning calorimeter (DSC). By satisfying both the MD heat shrinkage rate and the melting point, packaging bags can be produced that are suitable for bag manufacturing and have little deviation in size or pitch.

[0030] The thickness of the polyolefin film is not particularly limited. Depending on the application, the thickness can be 6 μm or more, preferably 9 μm or more, and more preferably 12 μm or more. The thickness can also be 200 μm or less, preferably 50 μm or less, and more preferably 38 μm or less. Within this range, excellent impact resistance and excellent gas barrier properties can be obtained.

[0031] The resin constituting the substrate layer is not limited to petroleum-derived resins, and may be partially or entirely biologically derived resin materials (for example, biomass polyethylene using biomass-derived ethylene as a raw material). A method for producing biomass-derived polyethylene is disclosed, for example, in JP-A 2010-511634. The substrate may contain commercially available biomass polyethylene (such as Green PE manufactured by Braskem), or may contain mechanically recycled polyolefin made from used polyolefin products or resins (so-called burrs) generated during the production of polyolefin products.

[0032] The substrate layer may contain components other than polyolefin resin. Examples of such components include polyamide, polyethylene terephthalate, polyvinyl alcohol, and biodegradable resin materials (e.g., polylactic acid, polycaprolactone, polyhydroxyalkanoate, polyglycolic acid, modified polyvinyl alcohol, casein, modified starch, etc.). The substrate layer may also contain additives such as antistatic agents, ultraviolet absorbers, plasticizers, lubricants, and colorants. The amount of components other than polyolefin resin in the substrate layer is preferably 15% by mass or less, and more preferably 10% by mass or less, based on the total amount of the substrate layer.

[0033] The above-mentioned base layer can be preferably used as a base in a three-layer laminate in which a base is arranged in the outermost layer, or as a gas barrier base in a three-layer laminate or a two-layer laminate in which a gas barrier base of a gas barrier film layer is arranged in the outermost layer.

[0034] [Sealant layer] The sealant layer is a layer that provides heat sealing to the laminate and contains polyolefin. The polyolefin content in the sealant layer is, for example, 40% by mass or more, and 70% by mass or more. The upper limit may be 100% by mass or even 90% by mass. When the polyolefin content in the sealant layer is 70% by mass or more, the polyolefin content of the laminate (based on the total amount of the laminate) can be easily set to 90% by mass or more, making it easy to realize a monomaterial structure.

[0035] Polyethylene resin or polypropylene resin can be used as the resin material constituting the sealant layer. When the sealant layer is polyethylene, linear low-density polyethylene (LLDPE) can be used. Furthermore, for purposes such as providing rigidity, a co-extruded laminated film can be used in which the gas barrier layer 3 is made of high-density polyethylene (HDPE) or medium-density polyethylene (MDPE) and the content side is made of low-density polyethylene (LDPE). Furthermore, ethylene-based resins such as low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), linear low-density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, and ethylene-(meth)acrylic acid copolymer, as well as blends of polyethylene and polybutene, and polypropylene-based resins such as homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer, can be used alone or in a blend or co-extrusion laminate. The thickness of the sealant layer is, for example, 40 μm or more and 150 μm or less. The sealant layer may be made of biomass-derived polyolefin, such as a sealant film containing biomass polyethylene (for example, ethylene as a raw material) as a part or whole. Such a sealant film is disclosed, for example, in JP 2013-177531 A. The sealant layer may also contain mechanically recycled polyolefin made from used polyolefin products or resin (so-called burrs) generated during the manufacturing process of polyolefin products.

[0036] A packaging bag can be produced by placing the sealant layers of the laminate facing each other and heat-sealing at least a portion of their periphery. Examples of packaging bags include pillow bags, standing pouches, gusset pouches, three-sided sealed bags, four-sided sealed bags, and pouches with spouts (standing pouches, gusset pouches, three-sided sealed bags, etc.). Using a heat-resistant substrate can prevent pseudo-adhesion during bag production (defects in which parts stick together where they should not) and insufficient sealing strength due to insufficient bonding temperature or time due to a small difference in melting points between the substrate and the sealant. A polyolefin film is preferred as a highly heat-resistant substrate, and in particular, one with a nylon layer or a homopolypropylene layer on the substrate surface that will be the outermost layer of the laminate is preferred.

[0037] The difference in melting point between the sealant layer and the substrate is preferably 10° C. or more, more preferably 20° C. or more, and even more preferably 50° C. or more. The melting point of the sealant layer itself is preferably 140° C. or less, more preferably 120° C. or less. In addition to packaging bags, the laminate can be used in a variety of applications, including packaging products such as containers, decorative sheets, sheet-molded products such as trays, optical films, resin plates, various label materials, lid materials, and laminate tubes.

[0038] The laminate of the present invention may include an adhesive layer between the substrate and the gas barrier film layer, and between the gas barrier film layer and the sealant layer. The adhesive constituting the adhesive layer can be selected depending on the bonding method, and for example, a urethane adhesive, a polyester adhesive, an epoxy adhesive, etc. can be used. The provision of the adhesive layer increases the interlayer adhesion between the substrate and the sealant layer, or between the gas barrier film layer and the substrate, or between the gas barrier film layer and the sealant layer, making delamination less likely and maintaining the pressure resistance and impact resistance of the pouch. Examples of methods include a dry lamination method in which layers are bonded together using an adhesive such as a one-component or two-component curing urethane adhesive, a non-solvent dry lamination method in which layers are bonded together using a solvent-free adhesive, and an extrusion lamination method in which a polyolefin resin such as polyethylene or polypropylene is heated and melted, extruded into a curtain shape, and bonded together.

[0039] The adhesive layer preferably does not contain chlorine. The absence of chlorine in the adhesive layer can prevent the adhesive or recycled resin from becoming discolored or from generating odors due to heat treatment. From an environmental perspective, it is preferable to use an adhesive containing a biomass material as the adhesive layer. From an environmental perspective, it is preferable to use a method of adhesion that does not use a solvent.

[0040] [Gas barrier film layer] The gas barrier film layer includes at least a gas barrier substrate and a gas barrier layer, for example, a polyolefin film as a gas barrier substrate and a gas barrier layer formed by vapor deposition or coating.

[0041] Examples of the gas barrier layer include a gas barrier coating containing polyvinyl alcohol or the like, and a vapor-deposited layer of an inorganic oxide or metal. Examples of inorganic oxides include aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. Examples of metals include aluminum. Vapor-deposited layers can be formed by, for example, physical vapor deposition or chemical vapor deposition.

[0042] The gas barrier substrate can be made of the materials described above for the substrate layer. The thickness of the gas barrier substrate is, for example, 5 μm or more, or 10 μm or more. It may also be 800 μm or less, 500 μm or less, or 100 μm or less. The melting point of the gas barrier substrate can be measured using a differential scanning calorimeter (DSC). When the laminate is a three-layer laminate, the gas barrier substrate preferably exhibits a melting point similar to that of the substrate. On the other hand, the gas barrier substrate preferably has a melting point 20°C or higher, more preferably 25°C or higher, than that of the sealant layer. The melting point of the gas barrier substrate is preferably 120°C or higher, more preferably 125°C or higher.

[0043] When the laminate is a two-layer laminate, the gas barrier substrate can be made of a polyolefin having an MD heat shrinkage of less than 20%, preferably 15% or less, and more preferably 10% or less when heat-treated at 150°C. In this case, the melting point of the gas barrier substrate should be higher than that of the sealant layer, preferably 10°C or higher, and preferably 20°C or higher. The melting point of the substrate layer should be 150°C or higher, more preferably 160°C or higher. By satisfying both the MD heat shrinkage and melting point requirements, packaging bags can be produced with good bag-making suitability and minimal deviations in size and pitch. Polyolefin films are preferred as gas barrier substrates with high heat resistance, and in particular, those with a nylon layer or a homopolypropylene layer on the side of the laminate where the gas barrier layer, which is the outermost layer, is not formed are preferred. A specific example of a polyolefin with such physical properties is biaxially oriented polypropylene, which has high rigidity and high heat resistance.

[0044] Like the substrate, the material for the gas barrier substrate may be a polyethylene resin or a polypropylene resin. Similarly to the substrate, a biomass-derived resin or a mechanically recycled resin may also be used. Similarly to the substrate, the gas barrier substrate may contain components or additives other than the polyolefin resin, as long as they do not impair the recyclability of the laminated film. The gas barrier substrate may be subjected to a surface treatment such as corona treatment, ozone treatment, or flame treatment on the surface on which the vapor deposition layer is formed. From the viewpoint of heat resistance, it is preferable to use a stretched substrate as the gas barrier substrate. When a uniaxially stretched polyolefin is used, it is preferable to align the stretching direction with that of the substrate layer in order to maintain easy tearability.

[0045] The laminate according to the present disclosure may include an anchor coat layer (not shown) between the substrate and the gas barrier layer, between the gas barrier layer and the sealant layer, or between the substrate and the sealant layer. The anchor coat layer may be a very thin layer that does not affect the recyclability of the laminate, and can be formed using an anchor coat agent. Examples of anchor coat agents include acrylic resins, epoxy resins, acrylic urethane resins, polyester polyurethane resins, polyether polyurethane resins, and polyvinyl alcohol resins. From the viewpoints of heat resistance and interlayer adhesive strength, acrylic urethane resins and polyester polyurethane resins are preferred as anchor coat agents.

[0046] The thickness of the anchor coat layer is not particularly limited, but is preferably in the range of 0.05 μm or more and 2 μm or less. A thickness greater than 0.05 μm is expected to improve the adhesive strength between layers. A thickness less than 2 μm increases the proportion of polyolefin in the laminate, improving the recyclability of the laminate.

[0047] The laminate according to the present disclosure may further include a printed layer (not shown) of, for example, text information or a design, and gravure printing, flexographic printing, etc. are possible. In the case of a three-layer laminate, the printed layer may be provided between the substrate and the gas barrier film layer. In the case of a two-layer laminate, the printed layer may be provided between the gas barrier film layer and the sealant layer. The printed layer may be provided on the surface of the gas barrier substrate opposite the surface on which the gas barrier layer is formed. When a printed layer is provided, it is preferable to use a chlorine-free printing ink to prevent the printing ink components from discoloring or generating odors when remelted during mechanical recycling. From an environmental perspective, it is also preferable to use a biomass material as the binder component contained in the printing ink. Furthermore, the printing ink is preferably an aqueous ink using water or alcohol as the solvent, and it is preferable to use aqueous flexographic printing without using organic solvents from an environmental perspective.

[0048] One embodiment of the self-standing packaging bag according to the present invention is a gusset pouch. Fig. 5 is a schematic diagram of a spouted gusset pouch, which is one embodiment of the self-standing packaging bag according to the present invention. As shown in Fig. 5, the spouted gusset pouch 100 is made up of two side wall laminates 140 and two folded side wall laminates 150, with the peripheries of the side wall laminates 140 and 150 sealed. A spout consisting of a spout 104 and a cap 104a can be provided on the upper edge of the pouch body of such a gusset pouch to form the spouted gusset pouch 100.

[0049] Another embodiment of the self-standing packaging bag in a packaging form according to the present invention is a stand-up pouch. Fig. 6 is a schematic diagram of a stand-up pouch with a spout, which is another embodiment of the self-standing packaging bag of the present invention. As shown in Fig. 6, the stand-up pouch with a spout 200 is a packaging bag made up of two side wall laminates 201 and one bottom laminate 202 folded in half, with the periphery sealed. By providing a spout 203 consisting of a spout and a cap on the upper edge of the pouch body of such a standing pouch, it can be made into a stand-up pouch with a spout 200.

[0050] The side wall laminate 201 and the bottom laminate 202 of the spout-equipped standing pouch 200 may have the same laminate structure or different laminate structures. The structure can be adjusted depending on the type and weight of the contents.

[0051] The stopper, consisting of the spout and cap of the self-standing packaging bag according to the present invention, can be made of polyolefin. This allows the entire packaging body to be reusable. The stopper can be molded by a known molding method such as injection molding or compression molding. From the viewpoint of improving recyclability, polyethylene is more preferably used. The present invention will be described in further detail below based on examples. [Example]

[0052] Using the laminate according to the present invention, a side wall laminate and a bottom laminate for a standing pouch were produced as a self-standing packaging bag as follows. The present disclosure will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0053] Example 1 The substrate was a biaxially oriented polypropylene film A1 (thickness: 20 μm), and the gas barrier film was a silicon oxide vapor-deposited biaxially oriented polypropylene film (gas barrier substrate thickness: 18 μm). The gas barrier substrate was an OPP film on which an EVOH layer was formed by co-extrusion. An acrylic urethane coating was applied to the EVOH layer, and a transparent silicon oxide film 30 μm thick was formed using a vacuum deposition device with electron beam heating.

[0054] The substrate and gas barrier film were bonded together using an adhesive (Mitsui Chemicals, Inc., brand A626). The adhesive layer had a thickness of 3 μm. The gas barrier layer was placed on the opposite side of the substrate. Furthermore, linear low-density polyethylene B1 (thickness 60 μm) was bonded to serve as a sealant layer using an adhesive (Mitsui Chemicals, Inc., brand A626). The adhesive layer had a thickness of 3 μm. The laminate of Example 1 was a three-layer laminate consisting of substrate / adhesive layer / gas barrier film layer / adhesive layer / sealant layer.

[0055] Example 2 The substrate was a biaxially oriented polypropylene film A1 (thickness: 20 μm), and the gas barrier film was an aluminum oxide vapor-deposited biaxially oriented polypropylene film (gas barrier substrate thickness: 18 μm). The gas barrier layer was formed by applying an acrylic urethane coating to the gas barrier substrate, followed by a 15 μm thick transparent film made of aluminum oxide using a vacuum deposition device with electron beam heating.

[0056] The substrate and gas barrier film were bonded together using an adhesive (Mitsui Chemicals, Inc., brand A626). The adhesive layer had a thickness of 3 μm. The gas barrier layer was placed on the opposite side of the substrate. Furthermore, linear low-density polyethylene B1 (thickness 60 μm) was bonded to serve as a sealant layer using an adhesive (Mitsui Chemicals, Inc., brand A626). The adhesive layer had a thickness of 3 μm. The laminate of Example 1 was a three-layer laminate consisting of substrate / adhesive layer / gas barrier film layer / adhesive layer / sealant layer.

[0057] Example 3 Example 2 was obtained in the same manner as Example 1, except that a silicon oxide vapor-deposited unstretched polyethylene film (gas barrier substrate thickness 32 μm) was used as the gas barrier film layer. The laminate of Example 2 was a three-layer laminate consisting of substrate / adhesive layer / gas barrier film layer / adhesive layer / sealant layer.

[0058] Example 4 Example 3 was obtained in the same manner as Example 1, except that an unstretched polypropylene film B2 (thickness: 60 μm) was used as the sealant layer instead of the linear low-density polyethylene B1. The laminate of Example 4 was a three-layer laminate consisting of a substrate / adhesive layer / gas barrier film layer / adhesive layer / sealant layer.

[0059] Example 5 Example 3 was obtained in the same manner as Example 2, except that an unstretched polypropylene film B2 (thickness: 60 μm) was used as the sealant layer instead of the linear low-density polyethylene B1. The laminate of Example 5 was a three-layer laminate consisting of a substrate / adhesive layer / gas barrier film layer / adhesive layer / sealant layer.

[0060] (Comparative Example 1) A three-layer laminate of Comparative Example 1 was obtained in the same manner as in Example 1, except that biaxially oriented polypropylene film A2 (thickness 20 μm) was used as the substrate instead of biaxially oriented polypropylene film A1 (thickness 20 μm).

[0061] (Comparative Example 2) A three-layer laminate of Comparative Example 2 was obtained in the same manner as in Example 2, except that biaxially oriented polypropylene film A2 (thickness: 20 μm) was used as the substrate instead of biaxially oriented polypropylene film A1 (thickness: 20 μm).

[0062] (Comparative Example 3) A three-layer laminate of Comparative Example 3 was obtained in the same manner as in Example 3, except that biaxially oriented polypropylene film A2 (thickness 20 μm) was used as the substrate instead of biaxially oriented polypropylene film A1 (thickness 20 μm).

[0063] Comparative Example 4 A three-layer laminate of Comparative Example 4 was obtained in the same manner as in Example 2, except that the biaxially oriented polypropylene film A2 (thickness: 20 μm) was used as the substrate instead of the biaxially oriented polypropylene film A1 (thickness: 20 μm).

[0064] (Comparative Example 5) A three-layer laminate of Comparative Example 5 was obtained in the same manner as in Example 2, except that the biaxially oriented polypropylene film A2 (thickness: 20 μm) was used as the substrate instead of the biaxially oriented polypropylene film A1 (thickness: 20 μm).

[0065] (Comparative Example 6) A three-layer laminate of Comparative Example 6 was obtained in the same manner as in Example 1, except that an unstretched polypropylene film B3 (thickness: 60 μm) was used as the sealant layer instead of the linear low-density polyethylene B1.

[0066] (Comparative Example 7) A three-layer laminate of Comparative Example 7 was obtained in the same manner as in Example 1, except that an unstretched polypropylene film B3 (thickness: 60 μm) was used as the sealant layer instead of the linear low-density polyethylene B1.

[0067] The melting points of the substrate and sealant layer were measured using a differential scanning calorimeter (DSC). The melting points of the substrate and sealant layer and the difference between them are shown in Table 1.

[0068] [Table 1]

[0069] Using the laminates of Examples 1 to 3 and Comparative Examples 1 to 4, standing pouches were fabricated, each consisting of two side wall laminates and one bottom laminate folded in half, with heat-sealed edges. The standing pouches were 125 mm high, 95 mm wide, and 28 mm deep (depth of the valley fold of the bottom laminate). The results of bag production are shown in Table 1. A ◯ indicates a width deviation of 5% or less, a △ indicates a width deviation of 10% or less, and an × indicates a width deviation of 15% or less, relative to the standard value for the seal width on the side where the side wall laminates are bonded together.

[0070] Using the laminates of Examples 1 to 3 and Comparative Examples 1 to 4, two side wall laminates and one folded bottom laminate were heat-sealed at the periphery, and a polyethylene spout member was sandwiched and welded to produce a spout-equipped standing pouch. The packaging bags of Examples 1 to 3 were welded accurately, and the appearance of the bag was also good.

[0071] (MD heat shrinkage rate) The thermal shrinkage of the substrate was measured. A 150 x 150 mm mark was made in the center of a 250 x 250 mm film, which was then held in a 150°C oven for 5 minutes. After removal, the length in the MD direction was measured, and the shrinkage rate is shown in Table 1.

[0072] The oxygen transmission rate of the laminates of Examples 1 to 5 was measured at a temperature of 30° C. and a relative humidity difference of 70% according to JIS K7126-2:2006. The evaluation results are shown in Table 1.

[0073] The water vapor transmission rate of the laminates of Examples 1 to 5 was measured according to JIS K7129B at a temperature of 40° C. and a relative humidity difference of 90%. The evaluation results are shown in Table 1. Measuring device: Mocon water vapor transmission rate measuring device PERMATRAN-W3 / 33.

[0074] The results in Table 1 show that Examples 1 to 5 were able to provide packaging bags that maintained barrier properties. [Explanation of symbols]

[0075] 10, 20, 30...3-layer laminate, 40...2-layer laminate, 1...substrate, 2, 4...adhesive layer, 3...gas barrier film layer, 3a...gas barrier layer, 3b...gas barrier substrate, 5...sealant layer, 100...gusset pouch with spout, 104a...cap, 104...spout, 130...seal portion, 140...side wall laminate, 150...side wall laminate, 200...standing pouch with spout, 201...side wall laminate, 202...bottom laminate, 203...spout

Claims

[Claim 1] A laminate comprising at least a substrate layer and a sealant layer, the base layer is a polyolefin having an MD heat shrinkage rate of less than 20.0% when heat-treated at 150°C, the sealant layer is a polyolefin; the melting point of the sealant layer is lower than that of the base layer by 10°C or more; A laminate characterized in that the polyolefin content in the laminate is 90 mass % or more.

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